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Figure 4.
Figure 4. Interactions between KChIP1* and α1 and the
Common Binding Pocket Shared by NCS Proteins(A) Stereo view
through the hydrophobic pocket of dimeric KChIP1*-Kv4.2N30
complex. The H1 and N lobe are colored in cyan and C lobe in
black. H10 and α1 are green and brown ribbons, respectively.
Trp8 (W8), Leu9 (L9), and Phe11 (F11) are three key residues
interacting with hydrophobic pockets created by both subunits.
Red residues from bottom subunit (N lobe) interact with W8 and
F11 of α1 of the same subunit. Magenta residues from the top
subunit (H10 and C lobe) interact with L9 of α1 of the bottom
subunit. Phe81 (F81) and Phe82 (F82) in yellow from each subunit
interact together to form the other hydrophobic cluster and sit
next to H10-α1 helices. Red, magenta, and yellow residues form
a hydrophobic pocket surrounding two central helices, H10 and
α1. Bottom panel is the view rotated 85° around vertical
axis from view A, showing how the N lobe of the bottom subunit
and the C lobe of the top subunit together form the hydrophobic
pocket. At the H10-α1 crossing point, side chains of Ala2 (A2),
Ala3 (A3), and Ala6 (A6) of both α1 helices are displayed to
show the close contacts.(B) Common binding pocket shared by NCS
proteins. Surface maps, calculated from crystal structures with
H10 (gray helices) excluded for comparison, display the central
hydrophobic groove and conserved target binding pocket. All
structures are Ca^2+ bound. KChIP1*-Kv4.2N30 is the only peptide
bound binary complex structure, and the other three are just the
Ca^2+ binding proteins by themselves. Polar surface residues are
in gray and nonpolar surface residues are in yellow (inset). The
binding pocket for Trp8 and Phe11 (W8/F11 Pocket) and the
corresponding ones based on sequence homology on other NCS
proteins are in red (same residues in red boxes in Figure 1 and
Figure 4). The green helix is Kv4.2 α1 with W8 and F11 shown.
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